Parents of children with autism were roughly twice as likely to have been hospitalized for a mental disorder, such as schizophrenia, than parents of other children, according to an analysis of Swedish birth and hospital records by a University of North Carolina at Chapel Hill researcher and colleagues in the U.S. and Europe.

The study examined 1,237 children born between 1977 and 2003 who were diagnosed with autism before age 10, and compared them with 30,925 control subjects matched for gender, year of birth and hospital. The large sample size enabled researchers to distinguish between psychiatric histories of mothers versus fathers in relation to autism. The association was present regardless of the timing of the parent’s diagnosis relative to the child’s diagnosis.

“We are trying to determine whether autism is more common among families with other psychiatric disorders. Establishing an association between autism and other psychiatric disorders might enable future investigators to better focus on genetic and environmental factors that might be shared among these disorders,” said study author Julie Daniels, Ph.D., an assistant professor in the UNC School of Public Health’s epidemiology and maternal and child health departments.

“Earlier studies have shown a higher rate of psychiatric disorders in families of autistic children than in the general population,” she said. “We wanted to see if the parents of autistic children were more likely to be diagnosed with mental disorders.

“Our research shows that mothers and fathers diagnosed with schizophrenia were about twice as likely to have a child diagnosed with autism. We also saw higher rates of depression and personality disorders among mothers, but not fathers,” Daniels said.

This information will help researchers look among related diseases, such as psychiatric disorders, for causes of autism, Daniels said. “It may eventually help identify opportunities to prevent or treat the disorder.”

The study, “Parental psychiatric disorders associated with autism spectrum disorders in the offspring,” appears in the May 5, 2008, issue of the journal Pediatrics.

Coauthors of the study include Ulla Forssen, Ph.D., GlaxoSmithKline epidemiologist, Collegeville, Pa.; Christina Hultman, Ph.D., Sven Cnattingius, M.D., Ph.D. and Par Sparen, Ph.D., all of the department of medical epidemiology and biostatistics at the Karolinska Institutet, Stockholm, Sweden; David Savitz, Ph.D., director of the Center of Excellence in Epidemiology, Biostatistics and Disease Prevention, Mt. Sinai School of Medicine, New York; and Maria Feychting, Ph.D., Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.